Generally speaking, this invention relates to a stopper for closing containers. More particularly, this invention relates to a rubber/plastic stopper composite for use with evacuated tubes. Such tubes are particularly useful in taking blood samples from individuals for subsequent testing at a place separate from the place where the blood sample is taken. Accordingly, it is most important that the stopper provide superior sealing properties so that the evacuated nature of the tube is maintained until it is used, so as to obtain the proper quantity of a blood sample from the individual when the blood sample is being taken.
In the last several years, contamination from individuals in the environment where blood samples are being taken such as in a clinic, a doctor's office or in the hospital, has led to an increased use of single use throw away objects. That is, needles, syringes, lancets and any container containing a body fluid sample is used once and then discarded so as to avoid and/or reduce to a minimum the transfer of any disease from an individual from which a sample is taken to another individual, whether that individual is a technician of some kind or simply an individual handling used items in the vicinity where samples are being taken and/or tested.
One of the problems involved with the use of single use throw-away items is the fact that the cost of producing such items must be firmly controlled. For example, with respect to evacuated tubes for taking blood samples, many millions of such tubes are utilized on a yearly basis in the United States alone. Because of this, individual hospitals, in purchasing large quantities of such tubes, must take into consideration the cost. Thus, producers of such tubes must also take into consideration the cost in producing these tubes, and the materials involved.
One of the problems involved with evacuated tubes is producing stoppers for such tubes which will provide the necessary sealing properties to maintain the vacuum in the tube for a period of time sufficient to sustain adequate shelf-life prior to the use of the tubes. It has been found through many years of experience that elastomers such as natural and/or synthetic rubbers or a combination of these provide the best sealing properties between the cooperating surfaces of the stopper and the glass and/or plastic container. However, elastomers are relatively expensive in the quantities of stoppers used for throw-away evacuated tubes. Thus, many developments have been made in an effort to reduce the quantity of rubber used and to increase the quantity of thermoplastics which are, comparatively speaking, inexpensive. However, through many tests and use procedures, it has been found that plastics simply do not provide the same desired sealing properties for maintaining proper shelf-life of evacuated tubes.
In order to overcome the problems involved with the use of plastic as an inexpensive but less effective material, and rubber as a more expensive and much more effective sealing material, many developments have been made of combinations or composites of these materials to utilize plastic more and elastomer less. Representatives of such composite stoppers include, for example, the stoppers taught and claimed in the following U.S. patents.
U.S. Pat. No. 4,531,651 to Donnelly teaches a composite inner elastomer core and an annular surrounding plastic cap. This arrangement is appropriate for the purpose of reducing to a degree the amount of elastomer used. However, the thrust of the Donnelly patent is a particular complicated configuration of integral annular ridges in the plastic and the elastomer which cooperate with each other to hold the two parts together.
In this connection, in making literally millions of such stoppers, the molding procedures involved in producing such stoppers is also a very important price matter in the production. For example, any complicated or unusual arrangement of the various components that make up the composite increase the cost because molds have to be produced and maintained in order to make the complicated configuration of the sections making up the composite and the production line cost is increased if the complicated configurations require special handling arrangements to remove the molded parts from the mold, and to join them into the final composite. The Donnelly patent, for example, as mentioned above, includes cooperating annular ridges which hold the composite together and which increase the cost thereof because of these annular ridges. It should be borne in mind, when viewing the Donnelly structure, that a substantial amount of core in the form of an elastomer is still utilized for the composite taught and claimed in that patent.
A further stopper composite is taught in U.S. Pat. No. 3,499,568 to Riera. Riera teaches a composite in the form of two completely separate parts with an outer plastic part which is screwed onto the top of the container. Riera utilizes, therefore, the cooperating helical threads of the plastic and the container for maintaining his composite cap on his container. Riera recognized and uses a separate elastomer core portion for sealing the top of the container.
A further U.S. patent teaching a stopper composite is U.S. Pat. No. 4,465,200 which is a fairly recent patent covering a stopper composite and assigned to the assignee of this application. The invention taught in that patent is directed to a composite which provides for a well arrangement or a chamber in the top of the stopper which is formed by cooperation between the elastomeric core portion and the outer annular plastic cap portion to contain any blood droplets which may form on the top of the stopper when a blood sample is removed from the container. Again, cooperating flanges are formed on each portion of the composite in order to hold the composite together, and these cooperating flanges have the effect of involving a substantial cost in the formulation of the molds which make up each portion of the stopper, which comprises the ultimate composite stopper.
A further composite stopper development is taught in European Patent Publication No. 0150172 which is an invention of Konrad and assigned to C. A. Greiner and Son, Inc. The arrangement taught in this patent is a further very involved configuration wherein cooperating wedges on the inner elastomer core and the outer annular plastic cap serve to hold the two parts together. This arrangement, again, involves expensive utilization of molding and production facilities in order to provide the arrangement to complete the ultimate composite desired.
With the arrangement of this invention, by contrast, a composite stopper is provided which reduces to a minimum a quantity of elastomer utilized for providing the sealing properties for a stopper for a evacuated blood collection tube. Moreover, the cooperating structure utilized for holding the outer annular plastic cap together with the inner elastomer core is an extremely simplified arrangement of a plurality of circumferentially spaced holes placed or formed in the outer annular cap. These holes have the effect, when the composite is placed together, of providing a plurality of circumferentially spaced cooperating surfaces between the outer annular thermoplastic cap and the elastomer core. Placed in these cooperating surfaces is an adhesive material. That is, the Applicant herein has recognized and utilized the property of a conventional adhesive material which will adhere much more readily to an elastomer than to a thermoplastic material. For this reason, the holes formed in the plastic cap extend through the cap to the top surface of the elastomer so that once the two parts are joined together as a composite, the adhesive material merely has to be applied in one step to join the parts mechanically together utilizing the adhesive for this purpose. What is obtained is a relatively inexpensive, easily molded composite stopper for evacuated tubes of simplified configuration and construction. Nevertheless, the composite of the invention serves to properly seal the evacuated tube and to maintain proper shelf-life for an extended period of time until the tubes are actually used.